Over the past several years, local area networks (LANs) have become commonplace in business and manufacturing facilities. In the residential environment, though, stand-alone computers are common, but networked personal computers (PCs) have remained relatively rare. However, as consumers rely more heavily on personal computers to telecommute, shop, and interact with the ever increasing number of on-line services, home computer networks will become more desirable. This trend may be further augmented by the development of xe2x80x9csmartxe2x80x9d appliances, alarm systems, etc., which may be controlled by a home computer system. In addition, xe2x80x9cnetwork computersxe2x80x9d (NCs), which are inexpensive networked terminals without significant local memory or magnetic storage media have recently been introduced. These devices will make available inexpensive means of accessing data and programs on a remote personal computer, thereby reducing the investment in hardware necessary to create a home computer network.
Although the utility of home computers is increasing, and the cost of network hardware is decreasing, another major expense in the creation of such a home computer network resides in outfitting the home with network cabling to interconnect the desired PCs, NCs, appliances, and other network compatible devices. This expense, of course, is not affected by reductions in the price of the computer hardware itself. The expense of installing LAN wiring is generally less of a problem when creating LANs in office buildings. In the commercial and manufacturing environment, office facilities are often pre-wired with excess telephone cable. Unused telephone cable can therefore be used to support, for example, a 10 BASET local area network. It has also become more common to pre-wire business and manufacturing facilities with the dedicated LAN communication cable necessary to support local computer networks.
New residential construction generally does not include any pre-wiring of LAN cabling, and although telephone wiring is typically routed to many rooms of the house, there is generally no excess telephone wiring which can be dedicated to use in a local computer network However, over 60% of the homes in the United States are wired for cable television reception, providing a wide-band and potentially very high capacity information pipeline into a majority of American homes. This fact is currently motivating the development of interactive communication on the cable television infrastructure. In some cable television distribution systems, downstream communication from the cable service provider is carried on 6 MHz channels in the 50-750 MHz range. Upstream communication from the customer to the cable service provider is supported on several 6 MHz channels in the 5-42 MHz range. Over these communication channels, interactive services may be provided which include analog telephone service, as well as two-way digital communication such as access to the Internet, electronic shopping, videoconferencing, and other communication services. Cable modems, commercially available, for example, as the model CyberSURFER(TM) from Motorola, are designed to implement such two way digital communication between a consumer""s personal computer and the cable television service provider along the cable television line. As this trend continues to develop, consumers may connect more digital computing devices to their cable television wiring.
However, the use of this CATV wiring to support a local area network has not been previously accomplished As is described in detail in U.S. Pat. No. 5,255,267 to Hansen et al., it is possible to inject broadband video channels onto LAN cabling carrying thin Ethernet baseband communications. However, this requires that baseband signal energy at frequencies up to 25 MHz be blocked from entering the broadband video feed by a high pass filter. This filtering eliminates the possibility of sending upstream messages from the home to the cable service provider at, for instance, the 5 to 11 Mhz upstream channel currently supported by cable television service providers. Furthermore, typical baseband transceivers are designed to operate with twisted pair cable or 50 ohm coaxial lines, not the 75 ohm coaxial cable pre-installed in homes and used for cable television delivery.
The creation of a home personal computer network has thus entailed a significant amount of cable routing through interior walls of the household, which is a time consuming and expensive procedure. What is needed therefore, is a system and method of creating a home personal computer network without the necessity of installing dedicated network cabling.
In one embodiment, the present invention includes a communication system comprising an upstream source of broadband communications and a downstream local area network. The upstream source of broadband communications is coupled to the downstream local area network through a notch filter. Other embodiments of the present invention include a local-area-network of computing devices comprising a notch filter comprising a first port and a second port, wherein the first port is coupled to a first cable and the second port is coupled to a second cable. In addition, the first port comprises an input port for signals carried by the first cable, and the second port comprises an output port coupling notch filtered signals to the second cable. A plurality of computing devices are coupled to the second cable.
The invention also comprises methods of interconnecting computing devices. One method comprises receiving a signal comprising a plurality of cable television channels from a first coaxial cable, filtering out a portion of that signal to produce a filtered signal, and coupling the filtered signal to pre-installed cable television wiring. A plurality of computing devices are coupled to the pre-installed cable television wiring, which then communicate messages by modulating a carrier having a frequency within the filtered out portion.
A notch filter comprising a first port adapted for connection to a video distribution system and a second port adapted for connection to a local-area-network are also provided by the invention, as are new computing devices. Such computing devices may comprise first and second receivers, each configured to receive a broadband signal in the frequency band from approximately 50 to 750 MHz. Also, the computing devices may comprise first and second transmitters, wherein the first transmitter is configured to transmit a broadband signal in the frequency band from approximately 5 to 42 MHz, and the second transmitter is coupled to transmit a broadband signal in the frequency band from approximately 50 to 750 MHz.